Tag Archives: carnivorous plants

It commonly chances that I make my most interesting botanical discoveries when I am in a thrilled and expectant mood…some rare plant which for some reason has occupied a strangely prominent place in my thoughts for some time will present itself. My expectation ripens to discovery. I am prepared for strange things.

~Henry David Thoreau, 1856

The strange and miraculous Venus flytrap was the subject of the last post. But, North Carolina is home to a variety of other carnivorous plants, and we saw many of them on our recent trips to the Green Swamp and Holly Shelter. Here is a quick summary of some of these amazing insect-eating flora…

Butterwort flower and leaves (click photos to enlarge)

Butterworts – Pinguicula sp.- Latin, pinguis, means fat. Common name refers to glistening leaves. Three species of this plant equivalent of flypaper are found in NC.

Blue butterwort, Pinguicula caerulea

Yellow butterwort, P. lutea

Small butterwort, P. pumila

Basal rosette of butterwort leaves act like flypaper

The leaves of butterwort use two specialized glands, scattered across the leaf surface, for prey capture and digestion:

Close-up of butterwort leaves

1) a peduncular gland, consisting of a few secretory cells on top of a single stalk that produce a mucilaginous secretion that traps insects; 2) sessile glands, which lie flat on the leaf surface and release enzymes that digest soft parts of the insect body. These fluids are then absorbed back into the leaf surface through holes. Butterworts produce a strong bactericide which prevents insects from rotting while they lay exposed on the leaves and are being digested. This property has long been known by northern Europeans, who applied butterwort leaves to the sores of cattle to promote healing.

Bladderworts are the largest genus of carnivorous plants with over 200 species worldwide. About 16 species are found in NC with most found in the Coastal Plain. Most are aquatic or occur in wet soils. They lack roots, but they do have underground or underwater stolons (creeping plant stems) that behave as roots.

The most common bladderwort we saw was the tiny terrestrial species, U. subulata, that grows in wet sand

Bladders are scattered along the length of the plant under water (or wet soil) suspended from small stalks. Each is concave, under pressure, and sealed by a trapdoor kept watertight by a mucilaginous sealant. One touch of the tiny trapdoor trigger hairs, and the door swings open sucking prey and surrounding water into the low-pressure trap. Their traps suck in prey in less than one one-hundredth of a second, making this one of the speediest movements in the plant world. Once the prey is inside, a swirl of water pushes the door back again and the prey is trapped. Glands on the the inside of the bladder secrete enzymes that dissolve soft-bodied prey within hours. Other cells transport water back out of the trap, and it is reset.

Sundews in a roadside ditch

Sundews – Drosera sp. – Greek for dewy. One of the most abundant groups of carnivorous plants with over 160 species worldwide. There are five species in NC.

Close-up of a leaf of D. intermedia

Leaves lure, capture, and digest insects using stalked mucilaginous glands covering their leaf surfaces. These hairs trap insects in the sticky “goo”, and then proceed to digest them.

Leaves often curl to help pool the released enzymes and nutrients

Sundews move their tentacles toward their prey, causing them to get even more stuck.

Even the flower stalks and buds of D. brevifolia seem to trap small flying insects

Enzymes dissolve the prey and released nutrients are then absorbed through the leaf surface.

Yellow pitcher plants at Holly Shelter Game Lands

Pitcher plants – Sarracenia sp. – After Michel Sarrazin (1659–1735), the first naturalist to send pitcher plants to Europe for study. Pitcher plantsare passive pitfall traps (they don’t move). Pitchers are modified leaves and many species have lids or hoods which keep out rainwater.

Yellow pitcher plant leaf before the trap tube opens

Prey are lured by nectar and colors/patterns on the pitcher that mimic a flower. At least one species, S. flava, has a toxic alkaloid in the nectar that may intoxicate prey.

Dissected pitcher showing downward pointing hairs and prey

Prey fall into the trap due to the slippery inner wall of the upper section. Narrowing diameter of the tube and downward pointing hairs in lower portions further inhibit escape. Digestive enzymes are secreted and nutrients are absorbed by the plant tissues.

Purple pitcher plants lack a lid and collects rainwater

Prey are believed to drown in the open pitcher of purple pitcher plants, S. purpurea. Microorganisms living inside the pitchers contribute to decomposition and nutrient uptake by the plant. If you look inside one of these pitchers, you may see things swimming in what you would think would be a deadly soup. We pulled a turkey baster full of liquid out of one pitcher and found both prey remains and living organisms that use it as a home.

The material siphoned out of a purple pitcher plant pitcher…yellow lines indicate a live mosquito larva and pupa; the blue line is a live midge larva

The larvae of a small, non-biting mosquito (Wyeomyiasmithii) and a midge (Metriocnemusknabi) live in the liquid in the pitcher, somehow withstanding the digestive enzymes that kill other insects.

This has been a quick glimpse into the lives of these strange and wonderful plants. I have so much more to learn about these amazing plants and their specialized adaptations for surviving in nutrient poor soils in these intriguing habitats.

The great wonder of the vegetable kingdom is a very curious unknown species of Sensitive. It is a dwarf plant. The leaves are like a narrow segment of a sphere, consisting of two parts, like the cap of a spring purse, the concave part outwards, each of which falls back with indented edges (like an iron spring fox-trap); upon anything touching the leaves, or falling between them, they instantly close like a spring trap, and confine any insect or anything that falls between them. It bears a white flower. To this surprising plant I have given the name of Fly trap Sensitive.

A couple of weeks ago I posted this image from an Educator Trek to Holly Shelter Game Lands and asked you to consider what these people were studying. It was one of the highlights of our session – examining the amazing carnivorous plant, the Venus flytrap, Dionaea muscipula.

The traps are highly modified leaves (note flower stalk emerging from center). These plants grow in moist, nutrient-poor soils, only within about a 75-mile radius around Wilmington, NC. The carnivorous habits are an adaptation to secure needed nitrogen from their invertebrate prey.

Each trap consists of two hinged lobes with a fringe of fleshy “teeth”.

On the inner surfaces of the lobes are trigger hair projections, called trichomes, that cause the lobes to snap shut when prey comes in contact with them.

Two trigger hairs must be touched by prey within 20 seconds (or one hair twice). The trap shuts rapidly (in less than a second).

When a non-prey object, like raindrops or a human with a pine needle, causes the trap to shut, it typically is loosely closed as in the photo above. If no other disturbance occurs to the trigger hairs, the trap will reopen within several hours. If, however, a prey item is caught, and is struggling and continues to hit the trigger hairs 4 or 5 more times, the trap shuts tightly and begins to release digestive enzymes. The enzymes gradually digest the soft parts of the prey. The nitrogen (and other nutrients) released are then absorbed by the lobes and the trap will reopen after several days. Each trap can open and close 4 or 5 times before that trap dies. New leaves with traps are then produced from underground stems.

A trap ready for a snack.

A recent publication on flytraps provides results of a collaboration between researchers at the NC Botanical Garden, NC State University, and the US Fish and Wildlife Service. They examined the diet of flytraps in the field to investigate if there is any overlap between their prey and their pollinators (which seems like a bad idea from the plants’ perspective). We decided to look for ourselves and see what we could find in a few of the traps.

We gently opened a few traps to see what they had eaten.

A spider (probably some sort of wolf spider) as prey in one trap.

Our limited results were in line with what the scientists found – 40% of the prey they found in traps were spiders. The second largest group of prey were ants. In other words, Venus flytraps seem to specialize in eating crawling invertebrates, whereas the pollinators they found were primarily flying insects (bees and beetles). This makes sense when you look at the architecture of this plant. Traps are low to the ground, rarely rising more than an inch or two off the substrate. In contrast, the small white flowers are borne on stalks rising about 12 inches above the traps, helping to ensure that the plant minimizes the risk to its flying pollinators. Perhaps a more appropriate name for this wonder would be “Venus spidertrap”.

Poaching Venus flytraps is now a felony in North Carolina.

After observing these botanical marvels, we can appreciate why Charles Darwin called them “the most wonderful plant in the world”. In recognition of its limited global range (primarily in NC) and concern over its conservation, North Carolina designated the Venus flytrap as the official state carnivorous plant in 2005. And, as of 2014, Venus flytraps are protected from poaching by a law that makes it a felony to dig them up in the wild. If you would like to learn more, and see some flytraps (and other insect-eating plants) up close, you can visit the carnivorous plant collection at the North Carolina Botanical Garden. They should be blooming soon!

Share this:

Like this:

Let us turn elsewhere, to the wasps and bees, who unquestionably come first in the laying up of a heritage for their offspring.

~Jean-Henri Fabre, entomologist, 1823-1915

They’re back…the wasps flying inside my office window like they did last year about this time. Except now, I knew to expect them and why they are there. Last year, I was puzzled when one, then two, then several small black wasps appeared in my office over a few days in April. After catching and releasing them, I noticed they were all alike, and not the typical paper wasp that occasionally gets inside to overwinter. These wasps had an extended thread-like waist. I soon guessed they must be coming from the dried pitcher plant leaves (pitchers) I had stored in my office. Garden staff collect these old leaves every winter and we use them in educational programming. When you cut open an old pitcher, you can observe the variety of insects that the pitcher plant consumed by examining the dried remains of their exoskeletons (the soft parts are dissolved by digestive enzymes from the plant, leaving behind the hard parts of the bugs like legs and wings). Of course, as has always been the case in my work life, storage is an issue, so I naturally have several bags of these pitchers sitting on a shelf in my office. And that is where the wasps are coming from.

After finding the wasps last year, I did a little research and found out my office mates belong to a group of wasps, known as grass-carrying wasps, that use hollow spaces (like the tubes of pitcher plants) for building their nests. They are members of the wasp family, Sphecidae, the thread-waisted hunting wasps, which provision their nests with prey ranging from spiders to caterpillars (depending on the wasp species). The familiar mud daubers are a relative of the grass-carriers.

Grass-carrying wasp on outside of dried pitcher plant in my office

In one of our school field trips this spring, a student showed me what she found when dissecting one of the dried pitcher plants – a wad of grass and a little “mummy”.

Wasp pupa with pupal case removed

I think she had accidentally pulled the wasp pupa out of its case as she tugged at the debris inside the pitcher plant. The grass is what these wasps use to construct their nest. The females collect grass stems and stuff them inside hollow spaces (pitcher plant leaves, old carpenter bee holes, or even the tracks of storm windows), creating a nest chamber. She then hunts for a prey item, usually a tree cricket, stings it in just the right spot to paralyze it, and brings it back to the nest. After securing it in the grass chamber, she lays one egg on the cricket, then seals off the nest with more grass. After the egg hatches, the wasp larvae eats the cricket and forms a pupa in the grass chamber. The adult wasp emerges and chews its way out of the nest (there are probably two generations per year in our area). They spend the winter as a pupa, emerging in spring (often, inside my office it seems). Not to worry, this species is non-aggressive, and would not sting unless you grab it, so they are easy to catch in a jar and release.

Grass plug sticking out of hole chewed in pitcher plant by a grass-carrying wasp

Last fall, I was leading a program when I spotted a blade of grass flying through the garden in the carnivorous plant collection. It was a female wasp carrying a 6-inch piece of dried grass to her nest. We watched as she landed on a pitcher plant and dragged the grass into it through a hole on the side. The next day I went back and photographed her handiwork, with several strands of grass poking out the side of the plant. A goal for this year is to get lucky and grab a photo of a wasp carrying a long strand of grass back to her nest.

Grass plug in an old pitcher plant tube in the Green Swamp

On a recent trip to the Nature Conservancy’s Green Swamp, I found an old yellow pitcher plant tube with a grass plug exposed where the pitcher had split. I gently pulled it out, hoping to find a pupa.

The plug was densely packed into the tube

Grass plug in hand

I teased the grass plug apart, but found it empty.

What looks like an old pupal case below the grass plug

Just below the plug, I found what looks like an open pupal case. Perhaps the wasp had already emerged. As I read more about these wasps, I learned that they will create a dense plug of grass in the hollow space as a plug to seal off their nest chamber and protect the developing young. I suppose that is what I found as the tight wad of grass. But, based on the presence of a couple of small flies at my office window last week, it appears that the grass-carrying wasp is itself occasionally parasitized by other species, much like its cousin, the mud dauber. I imagine it happens during the nest construction, with a parasitic fly sneaking in and laying her egg in the chamber while the female wasp is out gathering more grass or her tree cricket prey.

Hoping to photograph more of the life story of this beautiful wasp this year

Once again, a closer look at some odd incident has revealed a fascinating story of behavior and interconnections in the invertebrate world just outside my door (and inside my window). Hoping to see and photograph more aspects of this interesting insect thus coming year…stay tuned.

Part two of our quest for carnivorous plants took us first to the Green Swamp, a well-known NC Nature Conservancy preserve site in Brunswick and Columbus counties. It was getting late in the day, so we went straight to the main access point, a small parking area next to a borrow pit along Hwy 211. We hiked in along the trail, through a short stretch of dense pocosin vegetation, and out into the open longleaf pine savanna.

Longleaf pine savanna in the Green Swamp (click photos to enlarge)

What you find here often greatly depends on the fire regimen – the year after a burn can produce spectacular wildflowers and make it much easier to see any in bloom. From the looks of it, I am guessing it may have been over a year since this particular tract was burned, but we could see some scattered spots of color poking above the clumps of wiregrass, especially along the pocosin edge.

Grass pink orchid, Calopogon sp.

In addition to insect-eating plants, these pine savannas are well-known for their gorgeous orchids. Calopogon comes from the Greek words meaning beautiful beard, and refers to the bushy, yellow protuberances on the lip of this delicate orchid. These are designed to attract pollinators, thinking there might be a pollen or nectar reward, but it is a deception. The lip of the flower is hinged at the base, and when an insect lands, the lip drops and traps the insect among the flower parts, forcing it to wriggle its way out, and, in the process, hopefully pollinating the flower.

Yellow butterwort, Pinguicula lutea

Scattered along the edges of the savanna are small, bright yellow flowers of a carnivorous species, the yellow butterwort.

Basal rosette of a butterwort

The business end of a butterwort lies at the base, where a tight cluster of sticky leaves serves to trap small insects by means of tiny stalked glands covered in mucilage. Other glands release digestive enzymes to help dissolve the soft tissues of the prey, with the nutrient-rich juices being absorbed by the leaf to supplement its nitrogen supply in this nutrient-poor environment.

Pink sundew, Drosera capillaris

A similar, but more active strategy, is employed by another insect-eater, the sundews. Tiny rosettes of red leaves covered in what look like dew-covered hairs dot the moist soil in the savanna, especially any place that is muddy along a trail or ditch.

Close-up of a sundew leaf with a trapped insect

When a potential prey touch the stalked glands, it gets stuck in the “goo”. Adjacent tentacles move toward the prey, further entrapping it. Digestive enzymes are released and the rest is history.

We finally had to head back to camp, but a good day of carnivorous plant exploration with sundews, two species of pitcher plants, butterworts, two species of bladderworts, and some Venus flytraps. The next day would prove to be even better.

Longleaf pine savanna in Holly Shelter

I had heard about Holly Shelter Game Lands for many years, but never managed to visit until now. It consists of over 63,000 acres of mixed forest, pocosin, and other wetlands in Pender County. Since it is turkey season, we were advised to visit on Sunday when there is no hunting. We drove along miles of dirt roads to several spots recommended by a friend for their plant diversity.

Carolina wicky, Kalmia carolina

Horsesugar, Symplocos tinctoria

A few small shrubs adding splashes of color in the longleaf forests, including a Coastal Plain relative of mountain laurel, Carolina wicky (also known as Southern sheepkill). Small starbursts adorn another savanna shrub, horsesugar (aka sweetleaf).

Our first stop was amazing – hundreds of yellow pitcher plant flowers came into view as we approached a small pond. There was also the bright green of the emerging new leaves, so it was a perfect time to view this species.

An unopened pitcher leaf

It is easy to forget that in all of these carnivorous plants, it is the highly adapted leaves that are the trapping mechanism. In the case of the yellow pitcher plant, the leaf blade usually elongates a foot or more before the top splits open to form the deadly pitfall trap.

A leaf just beginning to split to form the pitcher

This pitcher has a hood (or lid) and usually has red veins that serve as nectar guides for potential prey, luring them deeper into the trap.

An open pitcher with an unwise fly

The trap is a simple one – lure your victim with nectar, a sweet reward concentrated along the rolled lip and down into the upper edges of the trap. Once inside, the walls of the pitcher change texture and become very slick, causing the insect to fall into the tube. Below the slippery zone, the walls have rows of down-ward pointing hairs that inhibit an upward escape. As the insect gets farther down into the trap, the tube narrows, making it more difficult for flying insects to use their wings to escape. Digestive enzymes at the base of the trap all but ensure the fate of the hapless insect.

Contents of two pitcher plants back at the NC Botanical Garden

A popular activity at work is for students to dissect old pitchers (last year’s leaves) and examine what the plant had for dinner. The enzymes only dissolve the soft tissues to release the needed nutrients, so the hard parts of prey remain – an assortment of wings, legs, and exoskeleton pieces. Coworkers gathered the insect parts from two pitcher plants in the Garden’s collection for the photo above: several moths (left side of photo); a cluster of flies (upper right); a wasp (top); some small beetles (lower right); and an assortment of unidentifiable wings, legs, and parts. A large amount of fine dust-like material from the trap is not shown in this picture. I need to collect a few dried pitchers from native habitats and see what the locals have been eating for comparison, but I have a feeling the menu could be similar based on that fly photo above. It was about to make a culinary misstep.

Purple pitcher plant, Sarracenia purpurea

Purple pitcher plants lack a lid and their pitchers usually contain rainwater. Prey fall into the pitcher and drown. Ironically, there is a species of mosquito, Wyeomyia smithii, whose larvae live in these pitcher plants and feed on the microscopic community that exists in the water.

Possible hybrid pitcher plant

We did see a few pitcher plant clumps that looked like hybrids between the purple pitcher plants and the yellow. The pitchers look like the S. purpurea, but are much more elongate, like an S. flava. The flowers also seem to be a combination of the colors of the two species – both maroon and yellow tints.

Spoonleaf sundew, Drosera intermedia

Along the path were large numbers of the pink sundews we had seen in the Green Swamp, but the edge of the pond had another species. The spoonleaf sundew is more upright in growth form and seems to do well extending out into the water’s edge.

A tiny insect trapped in the sticky goo of the sundew

I leaned down for a closer look and could see more victims that had fallen for the glistening droplets that adorn these deadly tentacles.

Blue butterwort, Pinguicula caerulea

The Holly Shelter sites held two more species of butterwort – the blue and the correctly named small butterwort. The latter (which I failed to get a good photo of it turns out) has a pale, almost white flower, with a short flower stalk and a tiny rosette of leaves.

Blue butterworts were very common

The larger, blue butterworts, were quite common and often occurred in patches of twenty or more individuals, scattered about the various sunny locations we visited.

Venus flytraps, Dionaea muscipula, and a small purple pitcher plant

The Venus flytraps were amazing, as always, and abundant. Melissa mentioned all of these carnivorous plants in a recent post about one of her museum trips, so I won’t go into all the details of this, “one of the most wonderful plants in the world”, but I will share a few interesting tidbits.

Close-up of a flytrap leaf, showing the trigger hairs

The trap is a modified leaf and has 2 to 3 trigger hairs on each lobe of the trap. Two triggers must be touched in succession within about 20 seconds for the trap to “spring” (or one trigger twice). Closing in less than a second, the Venus flytrap is one of a group of very few plants capable of rapid movement (other local rapid movement plants include Eastern sensitive briar, Mimosa macrophylla, and bladderworts, Utricularia sp.). The fleshy “teeth” along the edge of the trap mesh together to form a closed cage around any prey (usually crawling insects and spiders). The whole trap squeezes together more tightly when the prey struggles. Enzymes are then secreted by minute glands on the inner surface of the lobes and the victim is digested over the next few days. Afterward, the trap reopens, awaiting its next target (each trap can only spring a few times before that leaf dies).

Emerging flytrap leaves

The name, Venus flytrap, refers to Venus, the Roman goddess of love. The genus, Dionaea, refers to Aphrodite, the Greek goddess of love and the daughter of Dione. The species name, muscipula, is Latin for mousetrap. It really is remarkable that the only place this amazing plant is naturally found is in about a 70-mile radius of Wilmington, NC. This trip proved to be one of strange beauties and incredible adaptations, and is definitely one we will do again.

Find one, and you’ll find yourself closer to the heart of what a Carolina Bay can be: an island of wildness in a world largely tamed, a few acres of the primeval past passed over by progress.

~T. Edward Nickens

The North Carolina Botanical Garden has an exquisite collection of carnivorous plants, and they are always a favorite stop on my programs. This encouraged me to revisit these mysterious beauties in their natural habitats in southeastern North Carolina. We got a few tips from our friend, Jerry, on some of the best locations, and headed out last weekend in search of insect-eating plants. This is part one of that exploration – the part we explored by kayak.

Afternoon paddle on Jones Lake (click photos to enlarge)

Our home for the weekend was the campground at Jones Lake State Park, a beautiful park centered on one of the many Carolina Bays that dot the landscape in this part of the state.

Google Earth view of the area showing a small portion of the estimated 900 elliptical Carolina Bays found in Bladen County.

These unique land forms attracted attention after the onset of aerial photography in the 1930’s, when thousands of ovals of varying size (there are an estimated 500,000), aligned in a northwest-southeast direction, could be seen dotting the Atlantic Coastal Plain from New Jersey to Georgia. The greatest concentration was in the Carolina’s. That fact, combined with their usual dominant vegetation of various bay trees, gave them their name. Few open water Carolina Bays remain, but even those that have been drained and developed, or have naturally filled with vegetation, are still visible as elliptical shapes in satellite images like the one above.

Many hypotheses have been proposed on the origin of Carolina Bays (including that they were formed by impacts of a meteor shower), but no single explanation is universally accepted. Many scientists now subscribe to the so-called oriented lake theory. It suggests that as the ocean retreated thousands of years ago, shallow pools of water remained throughout the Coastal Plain. Prevailing winds and resulting waves from the north elongated the ponds into their present elliptical shape. Whatever their origin, there is a large concentration of these bays in the Bladen Lakes area, and, fortunately, many are now preserved as state-managed lands.

Stunning sunset from our kayaks on Jones Lake

Cypress tree with Spanish moss at sunset

Our first evening, we paddled our kayaks around the lake and enjoyed a spectacular sunset all to ourselves among the scattered cypress trees along the eastern shoreline.

Melissa paddling Horseshoe Lake

The next morning we headed over to nearby Horseshoe Lake (aka Suggs Mill Pond). It is an aptly named shallow lake that is part of Suggs Mill Pond Game Lands, managed by the NC Wildlife Resources Commission. Suggs Mill Pond is an old millpond formed by damming a large peat-filled bay.

A sea of yellow pitcher plant flowers in the wetlands at Horseshoe Lake

It is spectacular this time of year as it contains thousands of yellow pitcher plants, Sarracenia flava. Their unusual flowers can be seen stretching across the wetlands along the lake edge.

Yellow pitcher plants in bloom along the shoreline

The new growth leaves that will form the pitchers are also visible, with many already opening into the deadly traps that will consume an array of insect prey over the next growing season.

Shed skin of a dragonfly where it transformed from an aquatic nymph into the winged adult

Sometimes the plants can serve as a place of “birth” instead of death. There were large numbers of dragonflies and damselflies on the wing and ample evidence of their amazing transformation from underwater predator to aerial acrobat scattered about on any upright surface sticking above the water – even on the flower of a pitcher plant.

White waterlily pads dotted the lake surface in many areas

One of the dominant plants in the lake was the beautiful white waterlily, Nymphaea odorata. The cleft leaves dot the surface with an array of colors, from green to red, and provide a place for all manner of creatures to sit upon the water.

Southern cricket frog, Acris gryllus

The repeated gick-gick-gick calls of Southern cricket frogs could be heard everywhere we paddled, along with the occasional katunk-katunk-katunk of carpenter frogs.

Male lilypad forktail damselfly

Delicate damselflies glided along our path, pausing briefly in their pursuits of prey, or each other, to rest upon a lilypad. The lilypad forktail is aptly named, as it almost always rests on lilypads, and characteristically touches the tip of its abdomen to the leaf surface.

The elegant flowers of the white waterlilies always tempt me to lean just a bit too far over the side of my canoe or kayak in order to capture their pleasing low-angle reflection.

Common grackle

We spotted several species of birds on the lake, including a green heron, red-shouldered hawk, northern parula warblers, Eastern kingbirds, wood ducks, mallards, and several common grackles busy setting up nest sites. This striking fellow allowed me to drift close enough to his perch to catch his iridescent colors…

Common grackle showing nictitating membrane

…and to see his “third eyelid”, the nictitating membrane.

Bladderwort flowers

In addition to the thousands of pitcher plants, another carnivorous plant species was incredibly abundant at this location – bladderwort, Utricularia sp.

Bladderworts, showing vegetative portions beneath the water surface

These mostly aquatic plants (there is a terrestrial species that occurs in moist sandy soils) have delicate flowers perched on slender stalks above the water, but the bulk of their biomass is beneath the surface. Scattered among the feathery vegetative portions, they have minute bladder-shaped organs with trap doors that can suck in tiny invertebrates that come in contact with the trigger hairs. Some areas of the lake had so much of this plant that it was like paddling through pudding at times as the vegetation clung to your paddle with every stroke. But, Horseshoe Lake is, nevertheless, a truly magical place, especially by kayak or canoe. Part 2 of our quest for the carnivores of the plant kingdom in the next post.

Like this:

“This plant, commonly called Venus’ fly-trap, from the rapidity and force of its movements, is one of the most wonderful in the world” and “is one of the most beautifully adapted plants in the vegetable kingdom.”

~Charles Darwin

One of the tree species Mike didn’t include on his recent tree bark quiz, probably because it’s much less common in our area than the loblolly pine, is the longleaf pine. It has the thickest and most resinous bark of any of our pines, the longest needles, and the largest cones. But perhaps most interestingly, at least to me, is the ecosystem that grows up around it.

Longleaf savanna in the Green Swamp Preserve

Longleaf forests once covered up to 60 million acres in the southeastern US, stretching from southern Virginia to eastern Texas. Early explorers and colonists saw dollar signs when they gazed upon the ‘endless’ forest: a source for all sorts of exportable products. The first major economic driver in North Carolina was the naval stores industry – the production of lumber, tar, pitch, and turpentine. Longleaf grow straight and true, making fantastic masts. Their resinous heartwood, called fatwood or lighterwood, was slowly burned under piles of earth, releasing pungent tar. Tar was boiled to thicken it into nearly-solid pitch. Tar and pitch were essential to the sea-worthiness of wooden ships: ropes and sails were soaked in tar, seams in the hull (and pretty much all other wood on a ship) were coated in pitch. The bark of living trees was scraped away, releasing the tree’s natural defense, resin, which was collected and distilled into turpentine. Turpentine had numerous uses, including as a remedy for colds (probably not the best idea). Though the longleaf forest must at first have seemed vast and limitless, after a century or more of harvesting, the once extensive blanket of longleaf pine in the southeast was reduced to about 3% of its original range.

Cat-faced tree in Croatan National Forest; longleaf trees were cut in a distinctive “cat face” pattern to promote the production and allow the collection of resin for distilling into turpentine and rosin.

I’ve never been a huge fan of pines. When I lived in Durham, my house was surrounded by huge loblollies, and the yard was ALWAYS covered in pine needles. But a trip to a longleaf pine savanna can change that perspective fairly quickly. Longleaf are so successful in their habitats that they form what at first seems to be almost a monoculture – longleaf, and only longleaf, growing rank on rank as far as the eye can see. They are straight trunked with a waving crown – their lower branches drop off as the tree grows. But if you look a little closer at the dense ground cover, you’ll soon find that the longleaf pine forest is a surprisingly diverse ecosystem.

Row upon row of longleaf, with a live oak standing out in the foreground. The oak is growing in a slightly wetter area at the edge of an ephemeral pool.

Some surveys of the ground cover in longleaf savannas have revealed more than 50 species of plants within one square meter. That is more diverse than a rainforest, at a small scale! And in North (and South) Carolina, we have some amazing species that live in that niche. Because of the nutrient poor soils found in longleaf habitats, plants need to have a good strategy for gathering the nutrients they need to thrive. Carnivorous plants have adapted some amazing ways to get nutrients from the ubiquitous insects that also live in this ecosystem. There are 4 primary groups of carnivorous plants in the savanna: sundews, butterworts, pitcher plants, and the most famous of all, the Venus fly trap.

When I saw my first fly trap, I must admit that I was a little disappointed. My high school put on “Little Shop of Horrors” when I was a student there, and Audrey was a pretty impressive, man-eating fly trap. In contrast, the traps of the real plants only get to be about 1 inch in diameter. But if you get down close to them and watch them in action, they are still impressive! The traps are actually modified leaves. They have green or red centers, the mid-rib of the leaf, each with 2-3 “trigger hairs” on the inside of the trap. The traps secrete sweet sap to lure their prey in and are rimmed with thin spines that will prevent escape. The spines look quite vicious, but are in fact more hair-like and won’t hurt you at all if you touch them. When an insect (or a pine needle yielded by a curious observer) touches two trigger hairs in quick succession, the leaf closes, trapping the insect. The repetition is important because the fly trap doesn’t want to be confused and close during every rainstorm! I hadn’t “tickled” a fly trap in a while, so on a recent trip to the savanna, I decided to try it out. Though I’ve done this before, I had forgotten just how quickly the leaf can close! Within less than 1 second it was shut. Apparently, this is one of the most rapid movements in the plant kingdom. Fly traps will reopen after a false trigger like mine, but it may take as much as a day for them to do that. And, they will only close so many times before turning black and dying, so it’s important not to “tickle” fly traps too often. But we typically encourage groups of teachers to try it, as it is an unparalleled educational opportunity to observe this amazing plant species. I filmed this video of a flytrap closing on a recent teacher workshop visit to a longleaf savanna.

Venus fly traps only grow within about a 100-mile radius of Wilmington, NC. Like longleaf, they depend on fire to keep their growing areas clear of taller species that will shade them out (more on fire later). They thrive in ecotones (areas of transition from one plant community to another) at the border between longleaf savanna and pocosins (shrubby bogs of the coastal plain). Because they are so interesting, and so rare, poaching has become a problem for fly traps. About two years ago, North Carolina increased the stakes for fly trap poachers – it is now a felony in NC.

Venus Fly Trap

But fly traps aren’t the only show in town. Other types of carnivorous plants also thrive at the edges of the pine savanna, including pitcher plants, sundews, butterworts, and bladderworts. The insect-trapping strategy for each of these is different. Pitcher plants lure insects inside and then trap them in their tubular leaves which are slippery and lined with downward-pointing hairs. The insects can’t escape and the plant exudes digestive juices to claim its nutrients. Purples pitcher plants, Sarracenia purpurea, are a little different – they drown their prey in pools of water.

The open leaves of the purple pitcher plant fill with water and drown insects… but inside of this one there was a small mosquito larva swimming around!

But even a pitcher plant can’t eat everything that falls in. Frogs sometimes hide out in them, a few species of caterpillar feed on the inner surface of the pitcher, and there’s even a species of wasp that lays its eggs in the shelter of the pitcher. Sundews look a bit like pin cushions that were left out overnight and have been coated by dew. The sweet-smelling droplets are both the lure for prey and the reason for its demise. It is entrapped in the sticky substance, and the leaf rolls up around it. The same sticky secretions also contain enzymes that digest the insect, providing the nutrients the plant is not getting from its environment.

Notice the vivid, red sundews and the sandy soil in which they’re growing.

We have 5 species of sundew in NC, 4 of which occur in eastern NC (the other prefers mountain bogs and a few sites in the Sandhills). I think this species is Drosera capillaris, but I’m not entirely sure without seeing a flower or seed.

Butterworts are a startling yellow-green color that stands out from the golds and browns of surrounding species in late winter/early spring. Their strategy for capturing prey is similar to sundews. They secrete a sticky substance on the surface of the leaf that lures, traps, ensnares, and digests small insects.

There are 3 species of butterwort reported in NC. According to Radford’s maps of their ranges, I think this is Pinguicula caerulea.

The final group of carnivorous plants found in this type of habitat are bladderworts. Bladderworts are the most varied (species-wise) of our carnivorous plants – there are 14 or 15 species in NC! The bladderworts I have seen in the past are aquatic. Their underwater roots have bladders that suck prey in to be digested. Apparently, there are also terrestrial bladderworts that live in boggy peat soils or moist sand. I didn’t realize this before my trip, so I’ll have to search them out when I return!

Though fly traps have the most limited range of our carnivorous plants, each type is remarkable in its own way and well-worth seeking out in some of the remaining longleaf pine savannas. They’re easy to miss when not in flower, but if you scour the edges where pocosin meets savanna, you might be fortunate enough to find some!